In the present industrial environment, there is a continuous need to have rugged and reliable machinery with a long lifetime, yet on the other hand, to have machinery that can be usable in a hostile environment which contains flying metal chips (e.g. from grinding and cutting operations) atmospheric particulate such as in a painting environment, and oil, and which has vibrations and other conditions harmful to machinery. There is also a need for machinery that can be used in such an environment, yet can be automatically controlled with a high degree of precision. In many cases, robots are being used in these environments to satisfy the conflicting requirements. Robots are used to perform simple and complex tasks, ordinary and dangerous functions, and brute strength movements of bulky and heavy components and precise manipulation of delicate parts.
Where robots are used, either tools are attached to movable robot arms or manipulators are attached to the arms so that objects can be grasped, lifted, and manipulated. However, there is the contradictory requirements of having a manipulator that is strong and able to grasp heavy objects with little deflection in order to maintain the accuracy, yet on the other hand still be lightweight itself, simple in design, compact in size, and accurately and repeatedly positionable with extremely small tolerances. At the same time, such a manipulator or gripper must be usable in the destructive environment that exists in the manufacturing locations.
The prior art discloses that one type of gripper usable with robots is comprised of two jaws that are relatively movable with respect to each other by a rack and pinion drive mechanism. One such example is disclosed in the Soviet Union Pat. to Baskarev No. 848,352 issued July 23, 1981. However, while the use of rack and pinion grippers satisfy many of the aforementioned requirements, they usually are deficient in their accuracy, responsiveness, and smooth action so that there is no binding and so that a known amount of operating torques can be applied to the gripper arms with a known applied force to the objects being gripped.